The present invention relates to a method for controlling delivery of liquid material to a semiconductor processing tool utilized in semiconductor processing.
Dispensing of slurry material to a platen of a chemical-mechanical polishing (CMP) tool from a delivery module is typically controlled by timed flow of material at a rate that is generally assumed to be constant. However, the assumption of an unvarying flow rate is often not accurate, due to issues such as partial obstruction of valves and tubing by viscous slurry material, and uneven pumping action by pumps.
Uneven flow rates over time can lead to inaccurate dispensing of CMP slurry to the platen. Often, this problem is addressed by utilizing an overly high flow rate to ensure that ample slurry is present on the platen. However, oversupply of CMP slurry needlessly increases the cost of the process by consuming excessive slurry material. This problem is exacerbated by the short lifetime of mixed slurry, which requires that the slurry be consumed shortly after its preparation from individual components
It is therefore desirable that structures and methods for precise dispensing of CMP slurry material during processing be developed.
In accordance with embodiments of the present invention, dispensing of slurry material to a CMP platen during processing is precisely metered utilizing closed loop control. Slurry material of known density is first supplied from a reservoir/mixing vessel to a dispense module. The dispense module receives a flow of an inert gas through a gas supply valve. Positive pressure arising within the dispense module due to the inert gas flow causes an outflow of slurry from the dispense module to the CMP platen. The rate of flow of the slurry to the CMP platen over time is determined by monitoring the change in weight of the filled dispense module. In a similar manner, variation in the rate of flow of slurry over time may be detected by monitoring weight change of the filled dispense module. A flow regulator structure in electronic communication with the dispense module and with the gas supply valve receives a first signal indicating the weight change of the dispense module. In response, the flow regulator structure communicates a second signal to the gas supply valve reflecting a change in the rate of flow of CMP slurry material to the platen. This second signal causes the gas supply valve to alter the flow of inert gas to the dispense module in order to correct for changes in the slurry flow rate.
An apparatus for dispensing material to a semiconductor processing tool in accordance with one embodiment of the present invention comprises a dispense module including a first port, a second port, and a third port, the first port in fluid communication with a reservoir and the second port in fluid communication with the semiconductor processing tool. A load cell measures a weight of the dispense module. A gas supply valve is in communication with a pressurized inert gas supply and with the third port of the dispense module. A flow regulator is in electronic communication with the load cell and in communication with the gas supply valve. The flow regulator is configured to receive a first signal from the load cell indicating the weight of the dispense module. The flow regulator is also configured to transmit a second signal to the gas supply valve. The second signal changes a state of the gas supply valve to correct a rate of flow of a processing material from the dispense module to the semiconductor processing tool.
A method for dispensing material to a semiconductor processing tool in accordance with one embodiment of the present invention comprises providing the material within a dispense module, and flowing an inert gas into the dispense module through a gas supply valve such that the material flows from the dispense module to the semiconductor processing tool. A flow rate of the material from the dispense module is detected by monitoring a weight change of the dispense module. Based upon the weight change of the dispense module, a signal is generated to alter the material flow rate. The signal is communicated to the gas supply valve to adjust the gas supply valve to compensate for one of an excessive material flow rate and an insufficient material flow rate.
These and other embodiments of the present invention, as well as its advantages and features are described in more detail in conjunction with the text below and the attached Figure.